Prior to this invention, automatically controlled top spin in combination with vertical oscillation by a tennis ball machine has not been effected. There has been need of economical means of providing vertical oscillation in combination with automatically controlled variable top spin to a tennis ball member propelled by a tennis ball ejector machine. The principal need for such a device is to provide tennis ball member trajectory to between the base line of a tennis court and near a tennis net on a receiver's side of the tennis court while automatically providing the required amount of top spin to prevent the tennis ball member trajectory going beyond a base line of the receiver's side of the tennis court before contact with the court's surface while simultaneously employing maximum ball velocity and lob height of the ball above the tennis net. The present invention is designed for attachment to existing or newly manufactured pneumatic type ball ejector machines employing a rigid barrel attached to a flexible air/ball conveyor hose with a collar attached to an adjustable bracket. This invention provides a greater variety of practice to all levels of tennis play for tennis players using above described tennis ball ejector machines prior to this invention. The present invention may be incorporated in the manufacture of new tennis ball ejector machines of the type described, whether or not having horizontal oscillating movement.